<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
		.box{
			width:300px;
			height: 300px;
			background: #eee;
			margin-left: 20px;
			margin-right: 30px;
			margin-top: 40px;
			margin-bottom: 50px;
			/*外边距连写*/
			margin:20px 30px 40px 50px;

		}
	</style>
</head>
<body>
	<div class="box"></div>
</body>
</html>